The present invention relates to a non-ejecting nozzle detecting method and device, and more particularly, to a method and device for detecting a non-ejecting processing liquid nozzle in an inkjet recording apparatus having nozzles that eject processing liquid for agglomerating colored inks.
Conventionally, when an image is printed on a recording medium in an inkjet recording apparatus, there has been a case in which water resistance of a recorded image is insufficient depending on a type of the recording medium.
In particular, when a color image is recorded, if a large quantity of ink is ejected on a recording medium in an attempt to print a high-density image, feathering may be caused depending on penetration of the ink into the recording medium. On the other hand, if it is attempted to print a high-density image while suppressing the penetration, a blur may be caused among inks of different colors. In both the cases, an image quality in printing a color image is substantially deteriorated.
Therefore, in recent years, in order to improve water resistance of a printed image and obtain a high-quality image (print) in an inkjet recording apparatus, a method of using processing liquid is proposed.
The processing liquid has an action of agglomerating and fixing color materials of colored inks. Therefore, when such processing liquid is used in the inkjet recording apparatus, before the colored inks are deposited on the recording medium, the processing liquid is deposited on the recording medium and the colored inks are deposited on the processing liquid. This makes it possible to prevent feathering and a blur of the colored inks on the recording medium and obtain a high-quality image.
In this case, usually, the processing liquid is deposited over an image recording area (image wise) of the colored inks on the recording medium by an inkjet head.
In ejecting the processing liquid, if there is a nozzle that does not eject the processing liquid among nozzles of the inkjet head, an area on which the processing liquid is not deposited is formed on the recording medium.
Naturally, if the colored inks are deposited on the area on which the processing liquid is not deposited on the recording medium, fixing and agglomeration of the color materials of the colored inks is insufficient. Therefore, desired ink density and a desired dot diameter are not obtained and the image quality is deteriorated.
In particular, when the inkjet head has a line head configuration, if a non-ejecting nozzle is present, the processing liquid is not deposited on an area on a recorded image and an image quality in the area is deteriorated, and hence the area appears like a line (streak) and is extremely conspicuous.
As the processing liquid, colorless and transparent processing liquid is used in order to accurately control color density of a recorded image area on the recording medium. Therefore, it is extremely difficult to detect whether or not the processing liquid is deposited on the recording medium, but it is extremely important in maintaining a quality of a recorded image to detect whether or not the processing liquid is deposited on an area on which the ink is to be deposited (image recording area).
Therefore, conventionally, there is known a technology of detecting the colorless and transparent processing liquid by performing test print prior to formal print.
For example, JP 08-118616 A discloses a method of forming comparing densities, hues, blurs, and the like of a line formed by depositing a colored ink one on top of processing liquid and a line formed by depositing only the colored ink, and detecting a non-ejecting nozzle using a result of the comparison. JP 08-118616 A also discloses a method of, after depositing processing liquid on a recording medium to form a stepped line, depositing a colored ink (solid deposited) over the entire surface of the recording medium, calculating density, a color, and the like of a line on which the processing liquid and the ink overlap, and detecting a non-ejecting nozzle using the density, the color, and the like.
JP 2004-223846 A and JP 2004-223847 A each disclose a method of, after depositing processing liquid and colored inks one on top of another to form dots and, on the other hand, depositing only the colored inks to form dots on a recording medium, calculating the density and dot diameters of the formed dots and detecting, using the density and the dot diameters, a non-ejecting nozzle that is not ejecting the processing liquid.
According to the method disclosed in JP 08-118616 A, a non-ejecting processing liquid nozzle can be detected. However, in the method of comparing a line formed by depositing processing liquid and colored inks one on top of another and a line formed by depositing only the colored inks, when the processing liquid and the colored inks are deposited one on top of another, if deposited positions of the colored inks are not extremely stable, it is extremely highly likely that some colored inks do not overlap the processing liquid and are not fixed. At the same time, only the colored inks are deposited to form a line, and hence an area in which the deposited colored inks are not fixed is formed on a recording medium.
Further, among the methods disclosed in JP 08-118616 A, in the method of, after forming a stepped line with processing liquid, depositing colored inks over the entire surface of a recording medium, an area without the processing liquid, that is, an area on which only the colored inks are deposited and are not fixed is formed in an extremely wide range on the recording medium.
If the recording medium having the area on which the colored inks are not fixed in this way is conveyed, conveying rollers and the like are contaminated by the unfixed inks.
Further, if the conveying rollers and the like for the recording medium are contaminated in test print for detecting a non-ejecting processing liquid nozzle, stains adhere to the recording medium in normal printing.
In the method disclosed in JP 08-118616 A, in order to detect that deposited positions of the colored inks fluctuate (positional shift), instead of an ink nozzle fluctuating in the deposited positions, it is necessary to determine anew, with respect to a processing liquid nozzle, an ink nozzle used in detecting a non-ejecting processing liquid nozzle. Therefore, association between processing liquid nozzles and ink nozzles has to be set again and takes time.
In the method disclosed in JP 2004-223846 A and JP 2004-223847 A, it is possible to detect a non-ejecting nozzle that is not ejecting processing liquid, but every dot has to be measured by the charge-coupled device (CCD) camera and compared with a predetermined reference value. Therefore, large cost and time are required to detect a non-ejecting nozzle.
Further, in the method disclosed in JP 2004-223846 A and JP 2004-223847 A, it is possible to detect that deposited positions of colored inks fluctuate, but, instead of an ink nozzle fluctuating in the deposited positions, it is necessary to determine anew an ink nozzle used in detecting a non-ejecting processing liquid nozzle. Therefore, association between processing liquid nozzles and ink nozzles has to be set again.